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Greater circadian misalignment predicts reduced REM sleep, which in turn predicts poorer extinction recall

In a randomized controlled trial of 42 healthy adults, greater circadian misalignment on Night 4 significantly predicted larger reductions in REM% and REM minutes. Reductions in REM minutes on Night 4 significantly predicted poorer extinction recall the following day, even after controlling for total sleep time and slow wave sleep.

Last updated: Aug 29, 2026โ€ข1 RCTsโ€ข๐Ÿ“– Read as article โ†’

Evidence Score

Evidence Score44/100
Human RCTโ˜…โ˜…โ˜†โ˜†โ˜†
Meta-analysisโ˜†โ˜†โ˜†โ˜†โ˜†
Mechanismโ˜…โ˜…โ˜…โ˜…โ˜…
Safetyโ˜…โ˜…โ˜…โ˜…โ˜†
Confidencelow

Study Evidence

Study 1. A preliminary investigation of the relationship between rapid eye movement (REM) sleep and fear inhibition processes in the context of circadian misalignment.

rct

Vuong V, McGlashan EM, Birch S, Acheson D, Kavaliotis E, Courtney JA, Risbrough VB, Drummond SPA ยท Psychological trauma : theory, research, practice and policy (2026)

Participants: 42
Duration: 4 nights
Intervention: Experimental circadian misalignment (two consecutive 4-hour phase advances) with or without melatonin (3 mg) administration, compared to normal control
Outcome: REM sleep percentage and minutes, fear-potentiated startle extinction recall
Effect Size: ฮ”Rยฒ = .12 for REM minutes predicting extinction recall
Population: Healthy adults (mean age 24.89, SD 5.11)

Result: In a randomized controlled trial of 42 healthy adults, greater circadian misalignment on Night 4 significantly predicted larger reductions in REM% and REM minutes. Reductions in REM minutes on Night 4 significantly predicted poorer extinction recall the following day, even after controlling for total sleep time and slow wave sleep.

PubMed: 42658639DOI: 10.1037/tra0002257

Mechanism Graph

Circadian misalignment leads to reduced REM sleep (both percentage and minutes)
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Reduced REM minutes on Night 4
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Poorer extinction recall the following day
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Impaired fear inhibition may increase risk for trauma-related psychopathology

Limitations

  • โš Small sample size (n=42) and preliminary nature of findings
  • โš Melatonin administration was not fully controlled for in the analysis of circadian misalignment effects
  • โš Only two consecutive phase advances may not fully represent real-world circadian disruption patterns

Frequently Asked Questions

What is the main finding of this study?โ–ผ

The study found that greater circadian misalignment leads to reduced REM sleep, and that reductions in REM minutes are associated with poorer extinction recall, a key process in fear inhibition.

How was circadian misalignment induced?โ–ผ

Circadian misalignment was induced by two consecutive 4-hour phase advances over four nights, with some participants receiving melatonin (3 mg) or placebo.

What was the sample size and population?โ–ผ

The study included 42 healthy adults with a mean age of 24.89 years (SD = 5.11).

What are the implications of this research?โ–ผ

The findings suggest that circadian misalignment, common in occupations with high trauma risk, may impair fear inhibition via reduced REM sleep, potentially increasing vulnerability to PTSD.

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References

  1. 1.Vuong V, McGlashan EM, Birch S, Acheson D, Kavaliotis E, Courtney JA, Risbrough VB, Drummond SPA. "A preliminary investigation of the relationship between rapid eye movement (REM) sleep and fear inhibition processes in the context of circadian misalignment.." Psychological trauma : theory, research, practice and policy, 2026. PMID: 42658639 DOI: 10.1037/tra0002257
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